Pepe has a history of aggressive play in the "clasico" series, including a red card in last season's Champions League semifinals, and the hot-tempered Portugal defender stepped on Messi's left hand in the 68th minute at the Santiago Bernabeu stadium.

Both Barcelona coach Pep Guardiola and counterpart Mourinho said they did not see the incident, but the Madrid coach said "if it's intentional then it's punishable."

"Unfortunately these are plays that are there but the referee didn't see," Barcelona midfielder Xavi Hernandez said. "That was brutal."

Pepe harassed Barcelona throughout the match, although a 17th-minute yellow card for barging into Sergio Busquets forced Madrid's aggressive defense to settle.

He was involved in a number of on-field clashes with Busquets and Cesc Fabregas before being substituted soon after the stamping incident, with Madrid's players growing increasingly frustrated as they stumbled to a ninth defeat in 13 matches against Barcelona.

Even Manchester United striker Wayne Rooney tweeted: "Pepe. What an idiot. Sometimes people wind u up."

But Pepe's exit eventually led to Barcelona's winner, as Messi played on and scooped a pass to Eric Abidal to score the 77th-minute winner for the Catalans ninth win in its last 13 matches against its archrival.

"The truth is that this is not the first time," said Barcelona defender Daniel Alves, who received Pepe's tackle in the first leg Champions League match in April that led to his eventual dismissal.